Defrost evaporator structure



June 9, 1959 T. A. MOGREW DEFIROST EVAPORATOR STRUCTURE Filed Nov. 25.1957 F' IG.2.

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THOMAS A MC GREW BY% m ATTORNEY 2,889,692 DEFROST EVAPORATOR STRUCTUREThomas A. McGrew, Fern Creek, Ky., assignor to General Electric Company,a corporation of New York Application November 25, 1957, Serial No.698,622

2 Claims. (Cl. 62-276) The present invention relates to an evaporatorstructure and is more particularly concerned with a roll-forged orroll-bonded evaporator including as an integral part thereof a closedliquid-vapor circuit and means for heating a portion of that circuit forthe purpose of periodically removing frost from the evaporatorstructure.

. A number of arrangements are known for employing what is sometimescalled a secondary defrost circuit for defrosting a refrigerantevaporator. These arrangements comprise a closed circuit or passagewaycharged with a volatile liquid and including a section in heatingrelation with the frosting portions of the evaporator and a vaporizingsection which when heated causes the hot vapors from the evaporatingcharge to circulate through the circuit and warm the evaporator todefrosting temperatures.

The application of this defrost scheme to a roll-forged or roll-bondedevaporator presents a number of problems in that the defrost circuitwhich must be separate from the refrigerant circuit, must neverthelessbe in heating relation therewith for proper defrosting action. Inaddition the defrost circuit must be in the form of a closed orcontinuous passage for continuous circulation of the defrosting vaporsand must be so constructed that the vapors formed in the vaporizingsection will not interfere with the continuous circulation of vapors andliquid in the defrost circuit.

It is a primary object of the present invention to provide a roll-forgedrefrigerant evaporator structure including separate circuit means foruniformly heating the structure to defrosting temperatures.

Another object of the invention is to provide an evaporator structureincluding a roll-forged evaporator having a serpentine refrigerantcircuit including a refrigerant accumulator and a separate defrostcircuit in the form of a closed double loop passage for periodicallyheating the entire evaporator structure for the purpose of removingaccumulator frost.

Further objects and advantages of the present invention will becomeapparent as the following description proceeds and the features ofnovelty which characterize the invention will be pointed out withparticularity in the claims annexed to and forming part of thisspecification.

In accordance with the present invention, there is provided arefrigerant evaporator structure comprising a rollforged evaporatorhaving formed therein a refrigerant circuit comprising a serpentineportion having a refrigerant inlet adjacent the top of the evaporatorand a refrigerant accumulator adjacent the lower portion. Since theevaporator structure is preferably of the roll-bonded or roll-forgedconstruction, the accumulator portion conveniently consists of aplurality of vertically and horizontally, extending intersecting tubularportions as is well known in the art.

As is well known, evaporator structures of this type can be formed bysuperimposing one metal plate on another with a predetermined pattern ofstop-weld material on one of the sheets, roll-forging the sheetstogether and finally expanding, by means of fluid pressure the portionsatcnt 2 of the sheets which were prevented from welding by the stop-weldmaterial, the pattern thereof being selected to form in the finalroll-forged product the desired refrigerant and other passes or tubes.

In order to provide means for periodically warming the roll-forgedevaporator structure for the purpose of removing any accumulated frosttherefrom there is pro- Vided a second or defrost circuit which isformed along with the refrigerant circuit during the roll-forgingprocess. A charge of volatile liquid, such as one of the well knownrefrigerants in an amount suflicient to fill the lower portion of thedouble loop defrost circuit arrangement and a heater for volatilizingthe liquid are employed to heat the entire evaporator structure todefrosting temperatures. Preferably, the heater is supported on theevaporator structure in heating relation with the accumulator and witheach of the interconnected loops so that each loop comprises a firstsection in heat exchange relation with the heater and second orcondensing section in heat exchange relationship with a portion of therefrigerant circuit. By this arrangement the defrost circuit in effectcomprises, in series connection, a first evaporator section in heatexchange with the heater, a condensing section in heat exchange with theupper portion of the refrigerant circuit comprising the serpentinepassages, a second evaporator section in heat exchange with the heaterand a second condensing section in heat exchange relationship with theremaining portions of the refrigerant circuit. By providing suitabletraps in the defrost circuit, circulation of the liquid and vaportherethrough upon energization of the heater can be controlled for flowin a predetermined direction to effect simultaneous heating of theevaporator structure at two diiferent areas upon energization of theheater.

For a better understanding of the invention, reference may be had to thefollowing description thereof when taken in connection with theaccompanying drawing in which:

Fig. 1 is a side view partially in section of a refrigerator cabinetincluding the evaporator structure of the present invention;

Fig. 2 is an enlarged elevational view of the evaporator structure;

Fig. 3 is a sectional View along line 3-3 of Fig. 2; and

Fig. 4 is a detailed view of the lower portion of the evaporatorstructure of Fig. 2.

Referring now to Fig. 1 of the drawing, there is shown a refrigeratedcabinet 1 including a food storage compartment 2 in which there isdisposed the roll-forged evaporator structure 3 of the presentinvention, this evaporator structure being in a vertical position andspaced slightly from the rear wall 4 of the food storage compartment 2.The refrigerated cabinet includes also a condensing unit comprising acompressor 5 and a condenser 6, the condenser being connected to theevaporator structure through a capillary tube 8 while the compressor 5is connected through a suction line 9 to the outlet end of theevaporator.

As is best shown in Fig. 2 the evaporator 3 is in the form of a plate 11made by the roll-forging method whereby the plate includes bothrefrigerant and defrost circuit passages. invention, the refrigerantcircuit includes an upper serpentine portion 12 extending from one edgeof the plate where it is connected to the capillary 8 downwardly inserpentine configuration to an accumulator which preferably comprises anupper section 13a and a lower section 1312. More specifically, theserpentine portion 12 of the refrigerant circuit comprises a pluralityof down-' wardly sloping passes 14 extending substantially across theface of the sheet or plate 11 and connected loop In the illustratedembodiment of the 15 so that refrigerant entering the serpentine portionof the circuit from the capillary 8 flows downwardly through the passes14 and connecting loops 15 adjacent the edges of the plate 11 and intothe first accumulator section 13a. This section is connected by aconduit 16 to the second accumulator section 13b which is in turnconnected by means of a vertically extending suction gas passageway 17to the suction line 9 at the upper portion of the plate 11. Asillustrated, the accumulator sections 13a and 13b are preferablycomposed of a plurality of vertically and horizontally extending andintersecting tubular passageways in accordance with the usual practicein the rollfor-ged evaporator art.

Also in accordance with the illustrated embodiment of the invention,there is provided a fan 19 driven by a motor 29 for circulating air fromwithin the storage compartment 2 upwardly between the evaporator 3 andthe rear wall 4 of the cabinet for the purpose of cooling the contentsof the cabinet by means of the circulating cooled air. The evaporator 3is provided with an aperture 21 to receive the fan 19 whereby all of theair passing upwardly behind the evaporator structure 3 is directed out-Wardly through the opening 21 and into the upper section of the storagecompartment 2 from which it flows through a louvered door 22 forcirculation downwardly over the shelves 23 provided in the storagecompartment 2.

During normal operation of the refrigerating system particularly whenapplied to a freezer structure, there is a gradual accumulation of froston the evaporator structure which must be removed to maintain thedesired operation eificiency of the system, and to eliminate manualdefrosting.

In accordance with the preferred embodiment of the present invention,defrosting of the evaporator structure 'is accomplished by means of aclosed double looped defrost circuit containing in the lower portionthereof a quantity of vaporizable liquid such as any of the well knownrefrigerants and means for heating the liquid to effect vaporizationthereof so that circulation of the vapors through the defrost circuitwarms the remaining portions of the evaporator structure to defrostingtemperatures. More specifically, the defrost circuit which is in theform of a continuous or closed tubular passage formed during theroll-forging of the, evaporator com- .prises a first loop 26 and asecond loop 27 each of which have their lower or evaporator orvaporizing sections 29 and 30 in heat exchange relation with a heater32.

More specifically, the defrost circuit comprises in closed seriesconnection a first vaporizing section positioned below the heater 32, avertical riser 33 extending up the right hand side of the evaporatorstructure, a condenser portion 34 comprising a plurality of downwardlysloping passages in parallel with the upper passes 14 of theserpentinerefrigerant circuit, a vertical return line 36 whichterminates in a connection to the second vaporizing section 3% disposedabove the heater 32. This much of the defrost circuit up to the secondevaporator section 30 comprises a first loop of the double loop defrostcircuit, the second loop comprising the vaporizing section 30, a riser38 and the second condenser portion 27 in parallel with the remainingserpentine passes 14, the second condenser section also including aconduit portion 4% extending below the accumulator 13a and connectingthe condenser portion 27 to the first vaporizing section 29. Liquidtraps 41 and 42 at the inlet ends of the two vaporizing sections 34 29prevent reverse flow of the volatile liquid within the defrost circuitwhen the heater 32 is energized.

From the above it will be seen that by the means of the presentinvention there is provided an evaporator structure of the roll-forgedtype in which the entire circuitry both for therefrigerant and for thedefrost liquidcan be formed readily by the roll-forging process sincethere is no-overlap or-crossing'of the two circuits. A specific featureof the invention is the arrangement of the defrost circuit withreference to the main circuit such that there is provided a double loopdefrost circuit with all of the connections between the vaporizingsections and the condenser sections of the loops arranged along onevertical edge of the evaporator structure leaving the remainder of thestructure available for refrigerant circuit.

Upon energization of the heater 32 both of the evaporator sections 29and 36 are warmed so that the volatile liquid contained therein isevaporated. Due to the pres ence of the traps 41 and 42 the vaporresulting from the evaporation flows from the evaporator sections 29 and30 and rises through the risers 33 and 38 to the upper portions of therespective condensing sections 26 and 27. There the vapors condense,making available the heat of condensation for the melting of frost onthe respective areas of the evaporator structure. The condensedrefrigerant in section 27 flows downwardly into the evaporator section29 and the condensed refrigerant in the condenser section 26 flowsdownwardly into the evaporator section 30 where the vaporization processis repeated. For the purpose of charging the defrost circuit an inlet 50thereto is formed during the roll-forging process at one edge of thesheet. After the defrost liquid is introduced this inlet is suitablysealed as for example by means of a plug 51.

In those applications where the cabinet air is drawn over the evaporatorsurface by means of the fan 19 there may also be provided a plurality ofapertures 45 at spaced points throughout the face of the plate wherebyair from the cabinet can be drawn over the different shelves and throughthe openings and into the space between the evaporator and the rear wall4 of the cabinet. Also in such an evaporator structure it may be founddesirable to connect the upper passes of the defrost circuit condensingsection 26 around the fan opening 21 by means of one or more verticallyextending passageways 46 which will serve to defrost more quickly theareas of the evaporator adjacent the fan opening.

With reference to Fig. 4 there is shown a further detail of theevaporator structure in which the lower edge of the structure is formedinto a pair of troughs 49 on opposite sides or faces of the evaporatorstructure to collect condensate flowing down the faces of the structure,it being understood that the water collecting in the troughs 49 issuitably disposed of outside the cabinet structure. This troughstructure for the roll-forged evaporator is formed in the same manner asthe tubular passages, that is by the use of a weld resistant materialwhich will prevent welding in this area and provide separable portionsforming the two side walls of the trough 49.

While there has been shown and described a particular embodiment of thepresent invention it will be understood that the invention is notlimited thereto and it is intended by the appended claims to cover allmodifications thereof within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A defrostable refrigerant evaporator structure comprising avertically arranged roll-forged evaporator having formed therein arefrigerant passage having an inlet and an outlet at the top thereof anda second passage separate from said refrigerant passage, saidrefrigerant passage including a serpentine conduit portion, anaccumulator portion below said serpentine portion and a vertical passageadjacent one edge of said evaporator terminating in said refrigerantpassage outlet, said second passage forming a double loop continuoustubular conduit and containing a charge of volatile liquid, one of saidloops including a serpentine section in heating relation with a part ofsaid refrigerant circuit serpentine portion the other of said loopsincluding a serpentine section in heating relation with. the remainingpart of said refrigerant passage both of said loops including lowersections adjacent said accumulator and vertical risers connecting saidserpentine sections and said lower sections disposed between saidserpentine portion of said refrigerant passage and said verticalpassage, a defrost heater supported on said structure in heatingrelation with said lower sections and said accumulator for heating saidaccumulator to defrosting temperatures and for causing said volatileliquid in said lower sections to vaporize and circulate through saidserpentine sections to Warm the remaining portions of said structure todefrost temperatures.

2. In a refrigerated cabinet, a defrostable evaporator structurecomprising a vertically arranged roll-forged evaporator in spacedrelation with one wall of said cabinet, said roll-forged evaporatorcomprising a refrigerant circuit and a second circuit separate from saidrefrigerant circuit, said refrigerant circuit including a serpentineportion having a refrigerant inlet thereto adjacent the top of saidevaporator, first and second horizontally extending enlarged portionsadjacent the bottom of said structure and spaced from one another, saidenlarged portions forming refrigerant accumulator chambers, said firstenlarged portion being connected to the outlet end of said serpentineportion, a passage extending along one vertical edge of said structurefor connecting said first and second enlarged portions, an outletpassage connected to said second enlarged portion and extendingvertically along the other vertical edge of said evaporator to the topof said evaporator, means for periodically heating said structure tomelt accumulated frost thereon comprising a heating element secured tosaid structure between said enlarged portions, said second circuit beingin the form of a closed double-loop continuous tubular passagesubstantially coextensive with said refrigerant circuit and partiallyfilled with a volatile liquid, said second circuit including in seriesconnection, a first substantially horizontal vaporizing section in heatexchange relation with said heater, a first condensing portionparalleling and in heat exchange relation with the upper part of saidserpentine portion, a second substantially horizontal vaporizing portionin heat exchange relation with said heater and a second condensingportion in heat exchange with the remaining portion of said refrigerantcircuit, said vaporizing sections being disposed between said heater andsaid enlarged portions and including traps to prevent reverse flow ofvapor in said defrost circuit upon energization of said heater.

References Cited in the file of this patent UNITED STATES PATENTS2,513,823 Shreve July 4, 1950 2,551,163 Rickert May 1, 1951 2,760,346Grenell Aug. 28, 1956 2,781,646 Buchanan Feb. 19, 7

